The demands placed on the exhaust-gas quality of internal combustion engines, in particular of internal combustion engines for driving motor vehicles, have steadily increased in recent years. In the case of diesel engines in particular, NOx emissions constitute a problem, which is counteracted by means of so-called SCR catalytic converters. In an SCR catalytic converter, environmentally harmful NOx is converted with the aid of NH3, which is supplied to the catalytic converter generally in the form of an aqueous urea solution, into N2 and H2O.
To supply the urea solution to the exhaust gases of the internal combustion engine, a dosing system is required, which conventionally comprises an electrically operated pump and an electrically actuated dosing valve. Such dosing systems are cumbersome and expensive to produce, assemble and maintain.
EP 1 878 920 A1 discloses a liquid pump having an inlet, an outlet, a pump chamber for receiving the liquid, and an actuator which is movable between a first position and a second position and which is designed to pump liquid from the pump chamber into the outlet. The inlet and the outlet are fluidically connected to a supply passage when the actuator is in the first position. The supply passage runs around the actuator in order to permit a transfer of heat from the actuator to the liquid.
U.S. 2007/0295003 A1 describes a high-pressure dosing pump which is designed to provide a reducing agent to an exhaust-gas reduction system. The high-pressure dosing pump has an electromagnet for driving a piston which is arranged in a movable manner in an inner bore of a valve housing of the pump. The inner bore has a pressure chamber with an inlet one-way valve and with an outlet one-way valve. Movement of the piston causes reducing agent to be supplied at high pressure to an injection nozzle. The injection nozzle is arranged at a location which permits a maximum reduction of undesired pollutants in the exhaust gases.